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2018 Offshore Technology Conference


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April 30 – May 3, 2018


NRG Park | Houston, TX

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Presentations and Papers

Damping Identification from Measurement of Axial Riser Response Data

by Scot McNeill, Matt Stahl and Kenneth Bhalla

May 1, 2018  | 2:20 P.M. – 2:45 P.M.

The current water depth record for offshore drilling is approximately 11,000 feet, with several energy companies having leases in substantially deeper waters. For a typical drilling riser and BOP stack, the first axial resonant period is approximately one second for each 2000 feet of deployed length, thus five seconds for 10,000 feet, six seconds for 12,000 feet, etc. Therefore a resonant condition will occur with vessel heave response in very deep water. The weight of a long drilling riser and BOP stack, together with large predicted dynamic loads can lead to significant restrictions on riser running and retrieval. Under resonance, the response levels are influenced greatly by the damping levels, which are uncertain. Total predicted damping from previously quantified sources is less than 1% critical. This work demonstrates that significantly more damping exists.

In this work, the damping ratio is identified for the first axial riser mode using several sets of measured riser response data. Data sets were obtained from several drilling rigs during riser deployment or retrieval at sites in various water depths, using an assortment of transducers and data acquisition systems. Within each data set, the deployed riser length varies over time…